Moving from principles to action for energy supply that mitigates
against climate change requires a long-term perspective. Energy
infrastructure takes time to build up; new energy technologies take
time to develop. Policy shifts often also need many years to take
effect. In most world regions the transformation from fossil to
renewable energies will require additional investment and higher
supply costs over about twenty years

development of global CO2 emissions

Whilst worldwide emissions of CO2 will almost double under the Reference Scenario, under the Energy [R]evolution Scenario they will decrease from 24,350 million tonnes in 2005 to 10,600 m/t in 2050. Annual per capita emissions will drop from 3.7 tonnes to 1.15 t. In spite of the phasing out of nuclear energy and increasing demand, CO2 emissions will decrease in the electricity sector. In the long run efficiency gains and the increased use of renewable electricity will even reduce CO2 emissions in the transport sector. With a share of 35% of total CO2 in 2050, the power sector will fall significantly but remain the largest source of emissions, followed by transport